In recent years, an intraocular lens that can be inserted through a small incision has been available and often used in the clinical setting as phacoemulsification technology prevails, such intraocular lens being provided for alleviating post-surgical astigmatism and invasiveness of surgical procedures, and made of soft materials such as foldable silicon, acrylic resin, hydrogel or the like.
Further, there have also been provided various intraocular lens insertion devices for inserting such foldable intraocular lens through a smaller incision on an eye ball. According to those intraocular lens insertion devices, an intraocular lens folded small is allowed to be pushed out and into an eye through an insertion tube having a cylindrical shape, thus making it possible to insert the intraocular lens into the eye through a significantly smaller incision as compared to a conventional case requiring a pair of tweezers to be used for insertion.
Insertion methods of the intraocular lens insertion devices are broadly divided into a group of screw-type (screw style) and a group of push-type.
A push-type intraocular lens insertion device allows an operator to sensuously press an operation portion with his/her grip strength against resistance such as friction or the like between the intraocular lens and an inner wall of the insertion tube, and allows a pressure thus applied to be transmitted to the intraocular lens so as to push the same forward (e.g., see patent documents 1, 2, 3). According to such push-type intraocular lens insertion device, an insertion operation of the intraocular lens is not only simple, but can be performed with one hand, thereby allowing the operator to use his/her free hand to perform other operations when performing the insertion operation. However, the intraocular lens needs to be moved forward while balancing the friction resistance between the intraocular lens and the inner wall of the insertion tube with the pressure applied to the operation portion, thus making it relatively difficult to control the pressure applied to the operation portion. Further, a nozzle provided on a distal end of the intraocular lens insertion device is the narrowest portion in the insertion tube through which the intraocular lens passes. In this sense, a load generated as the intraocular lens passes through the nozzle becomes large, particularly when releasing an intraocular lens with high power therefrom and when an inner diameter of the nozzle is made small so as to match a smaller incision. Therefore, there is a possibility that the intraocular lens may be abruptly released into the eye, and that eye tissue may thus be damaged.
On the other hand, a screw-type intraocular lens insertion device comprises a plunger and a main body that are screwed together like an external thread and an internal thread. Such screw-type intraocular lens insertion device allows the plunger and a rod for pushing the intraocular lens to move to a lens advancement direction when an operation portion on an end portion of the plunger is twisted (e.g., see patent document 4). According to those screw-type intraocular lens insertion devices, it is easy to control moving amounts of the plunger and the rod. In this sense, the intraocular lens can be prevented to some extent from being abruptly released into the eye, even when the load generated as the intraocular lens passes through the nozzle is large when releasing a thick intraocular lens and the inner diameter of the nozzle is made small. However, since both hands are needed to perform the insertion operation, operation of the screw-type intraocular lens insertion device is relatively more troublesome than that of the push-type intraocular lens insertion device to a certain extent.    Patent document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2000-516487    Patent document 2: Japanese Unexamined Patent Application Publication No. 2003-144480    Patent document 3: Japanese Unexamined Patent Application Publication No. 2004-351196    Patent document 4: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. Hei 11-506357